Securities - Distribution of maturities of debt securities with approximate yield of portfolio (Detail) $ in Millions	Jun. 30, 2023 USD ($)
Debt Securities, Available-for-sale [Line Items]
Available-for-sale amount within one year	$ 1,280
Available-for-sale yield within one year (percent)	0.16%
Available-for-sale amount after one but within five years	$ 6,130
Available-for-sale yield after one but within five years (percent)	1.98%
Available-for-sale amount after five but within ten years	$ 2,099
Available-for-sale yield after five but within ten years (percent)	2.14%
Available-for-sale amount after ten years	$ 19,552
Available-for-sale yield after ten years (percent)	2.34%
Total fair value within one year	$ 1,269
Total fair value after one but within five years	5,984
Total fair value after five but within ten years	1,984
Total fair value after ten years	17,022
Held-to-maturity amount within one year	$ 1
Held-to-maturity yield within one year (percent)	3.48%
Held-to-maturity amount after one but within five years	$ 815
Held-to-maturity yield after one but within five years (percent)	3.60%
Held-to-maturity after five but within ten years	$ 2,046
Held-to-maturity yield after five but within ten years (percent)	3.56%
Held-to-maturity after ten years	$ 10,566
Held-to-maturity yield after ten years (percent)	4.18%
Total fair value within one year	$ 1
Total fair value after one but within five years	797
Total fair value after five but within ten years	1,964
Total fair value after ten years	10,110
U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Available-for-sale amount within one year	$ 0
Available-for-sale yield within one year (percent)	0.00%
Available-for-sale amount after one but within five years	$ 3,814
Available-for-sale yield after one but within five years (percent)	1.65%
Available-for-sale amount after five but within ten years	$ 615
Available-for-sale yield after five but within ten years (percent)	1.56%
Available-for-sale amount after ten years	$ 2,941
Available-for-sale yield after ten years (percent)	2.71%
Held-to-maturity amount within one year	$ 0
Held-to-maturity yield within one year (percent)	0.00%
Held-to-maturity amount after one but within five years	$ 721
Held-to-maturity yield after one but within five years (percent)	3.74%
Held-to-maturity after five but within ten years	$ 1,176
Held-to-maturity yield after five but within ten years (percent)	3.72%
Held-to-maturity after ten years	$ 0
Held-to-maturity yield after ten years (percent)	0.00%
U.S. Government sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Available-for-sale amount within one year	$ 244
Available-for-sale yield within one year (percent)	0.98%
Available-for-sale amount after one but within five years	$ 1,629
Available-for-sale yield after one but within five years (percent)	1.96%
Available-for-sale amount after five but within ten years	$ 1,379
Available-for-sale yield after five but within ten years (percent)	2.24%
Available-for-sale amount after ten years	$ 6,266
Available-for-sale yield after ten years (percent)	1.75%
Held-to-maturity amount within one year	$ 0
Held-to-maturity yield within one year (percent)	0.00%
Held-to-maturity amount after one but within five years	$ 90
Held-to-maturity yield after one but within five years (percent)	2.39%
Held-to-maturity after five but within ten years	$ 863
Held-to-maturity yield after five but within ten years (percent)	3.31%
Held-to-maturity after ten years	$ 477
Held-to-maturity yield after ten years (percent)	3.11%
U.S. Government agency issued or guaranteed
Debt Securities, Available-for-sale [Line Items]
Available-for-sale amount within one year	$ 0
Available-for-sale yield within one year (percent)	0.00%
Available-for-sale amount after one but within five years	$ 68
Available-for-sale yield after one but within five years (percent)	3.21%
Available-for-sale amount after five but within ten years	$ 1
Available-for-sale yield after five but within ten years (percent)	5.55%
Available-for-sale amount after ten years	$ 10,331
Available-for-sale yield after ten years (percent)	2.59%
Held-to-maturity amount within one year	$ 0
Held-to-maturity yield within one year (percent)	0.00%
Held-to-maturity amount after one but within five years	$ 1
Held-to-maturity yield after one but within five years (percent)	8.32%
Held-to-maturity after five but within ten years	$ 7
Held-to-maturity yield after five but within ten years (percent)	6.52%
Held-to-maturity after ten years	$ 10,088
Held-to-maturity yield after ten years (percent)	4.23%
Obligations of U.S. states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Held-to-maturity amount within one year	$ 1
Held-to-maturity yield within one year (percent)	3.48%
Held-to-maturity amount after one but within five years	$ 3
Held-to-maturity yield after one but within five years (percent)	4.23%
Held-to-maturity after five but within ten years	$ 0
Held-to-maturity yield after five but within ten years (percent)	0.00%
Held-to-maturity after ten years	$ 0
Held-to-maturity yield after ten years (percent)	0.00%
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale amount within one year	$ 0
Available-for-sale yield within one year (percent)	0.00%
Available-for-sale amount after one but within five years	$ 0
Available-for-sale yield after one but within five years (percent)	0.00%
Available-for-sale amount after five but within ten years	$ 104
Available-for-sale yield after five but within ten years (percent)	4.15%
Available-for-sale amount after ten years	$ 14
Available-for-sale yield after ten years (percent)	5.38%
Held-to-maturity amount within one year	$ 0
Held-to-maturity yield within one year (percent)	0.00%
Held-to-maturity amount after one but within five years	$ 0
Held-to-maturity yield after one but within five years (percent)	0.00%
Held-to-maturity after five but within ten years	$ 0
Held-to-maturity yield after five but within ten years (percent)	0.00%
Held-to-maturity after ten years	$ 1
Held-to-maturity yield after ten years (percent)	7.74%
Foreign debt securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale amount within one year	$ 1,036
Available-for-sale yield within one year (percent)	(0.04%)
Available-for-sale amount after one but within five years	$ 619
Available-for-sale yield after one but within five years (percent)	3.94%
Available-for-sale amount after five but within ten years	$ 0
Available-for-sale yield after five but within ten years (percent)	0.00%
Available-for-sale amount after ten years	$ 0
Available-for-sale yield after ten years (percent)	0.00%